The Warriors will promote baby formula on their uniforms in a major new sponsorship deal - undermining the breast-feeding message in communities that could benefit most, say critics.

Under the three-year deal, formula-maker Fernbaby will sponsor the Junior Warriors next year, before becoming a full sponsor of the club's NRL team in 2014 and 2015, with its logos displayed on players' shorts.

Warriors chief executive Wayne Scurrah said the sponsorship was "an exciting new direction for us and for sporting brands in New Zealand", bringing a potential to expand the game into Asia.

He said he was not concerned about how breast-feeding advocates and the general public might react to the Fernbaby sponsorship.

The use of formula came down to "personal choice", he said.

But Infant Feeding Association national co-ordinator David Newton said the sponsorship was a shame, highlighting the imbalance in influence between the corporate proponents of formula and volunteer breast-feeding advocates.

"It's pretty much impossible to have a counter to that kind of marketing on a Warriors' uniform," he said.

He did not think the Warriors had an obligation to avoid publicly promoting formula, or that formula makers should be antagonised. But the "breast is best" message would be muddled, deliberately, in the marketing gimmicks used to sell the commercial baby products.

"They want you to think it's a magic powder that's going to make your kid into a Warrior," he said. "But it's just milk powder - one that's unbelievably expensive and with an extra gold label that means nothing."

Maori, Pacific Island and provincial communities that traditionally supported the Warriors would be targeted, he said. Their relatively poor health statistics would benefit from breast feeding, where possible, for two years.

Fernbaby assistant director John McCaulay said cans of the firm's product had "breast is best" written on them.

Many mothers did not have the option of providing full-time care for their infants, especially in China - a target market for New Zealand-based Fernbaby - where grandparents often took care of children while parents worked in other cities.

Announcing the Chinese-owned Fernbaby's sponsorship of the rugby league team, Mr Scurrah said there was potential to "take the Vodafone Warriors to Asia".

He said Warriors' co-owner Eric Watson had received an approach from someone who wanted to establish rugby league in Shanghai.